People who exercise are certainly healthier than those who don't, but do they actually live longer? A review published in the latest issue of the Journal of Aging Research says they do, by an average of around four years. But the review also suggests that the type of exercise could be just as important.

A team of researchers led by sports scientist Anne Reimer collected a truckload of data from a range of previous studies, all of which were geared toward investigating the relationship between physical activity and life expectancy. Interestingly, they found that "physical activity during leisure time seems to increase life expectancy more effectively than total physical activity." That means people who opted to exercise during their free time appeared to benefit from it more than those required to exercise — for their work, for example. One explanation for this observation could be that people who exercise recreationally are more likely to foster other health-conscious habits, like eating right and abstaining from cigarettes, "healthy behaviors" the CDC has long praised for their longevity-boosting benefits.

And here's another interesting result: the researchers write that "eleven case control studies on life expectancy in former athletes revealed consistently greater life expectancy in aerobic endurance athletes but inconsistent results for other athletes." In other words, endurance exercise like running, appear to be more beneficial than anaerobic exercise like power lifting.